1. Field of the Invention
This invention relates to improved processes and compositions for the electrodeposition of nickel and alloys thereof.
2. Brief Description of the Prior Art
It has been found that the presence of zinc impurities tends to produce plating defects during the electrodeposition of nickel electroplates using compositions containing primary and secondary brighteners. The problem is especially acute during plating when the secondary brightener is saccharin (o-benzoyl sulfimide). In this case inadequate basis metal coverage may occur in low current density areas; unsightly striated (ribbed) deposits may occur; and dark; thin non-metallic appearing deposits may be produced which not only detract from the final appearance of the article being plated, but may also interfere with the receptivity, appearance, luster, etc. of subsequent deposits such as chromium plate.
In order to overcome the deleterious effects of zinc in the presence of saccharin, the use of sulfonic acids or hydroxy-sulfonates has been used. While these compounds do reduce the problem, their use also reduces the overall brightness and leveling of the deposit. This results in having to use thicker nickel deposits or higher levels of the primary additives in order to obtain commercially acceptable deposits.
An alternative approach has been to replace saccharin with another Class I additive, i.e., sodium benzene sulfonamide or sodium toluene sulfonate. These Class I additives, while not as sensitive to zinc impurities as is saccharin, are inferior to saccharin with respect to stress reduction, luster building (in cooperation with Class II additives), and sulfur contribution (especially important in duplex plating).